Rename the "All tasks" tab to "Explore"

Also refreshed web/README.md while touching this section: fixed the
project/project-configure header descriptions to describe the current
inline .title-back arrow (they still described the old separate "Back
to project" button), and added a "Card detail" section documenting
CardView/CardConfigureView/CardManageMenu, which had none.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/views/ProjectView.vue

@@ -21,9 +21,9 @@ const statuses = ref<CardStatus[]>([])
 const loadError = ref<string | null>(null)
 const actionError = ref<string | null>(null)
 
-// Tab order is unchanged (All tasks first); Kanban is just the default view.
+// Tab order is unchanged (Explore first); Kanban is just the default view.
 const tabs = [
-  { key: 'all', label: 'All tasks' },
+  { key: 'all', label: 'Explore' },
   { key: 'kanban', label: 'Kanban' },
 ] as const
 const activeTab = ref<(typeof tabs)[number]['key']>('kanban')
@@ -191,7 +191,7 @@ async function onCreateInColumn(column: Column) {
         </button>
       </div>
 
-      <!-- Tab: All tasks -->
+      <!-- Tab: Explore -->
       <div v-show="activeTab === 'all'" class="tabs__panel" role="tabpanel">
         <p class="muted">{{ summary }}</p>